In a bladed architecture environment, even airflow across a system is very important for the convective cooling of all blades in the system. Specifically, in a conventional computer chassis/card cage assembly, multiple slots are available to receive a corresponding printed circuit assembly (PCA). Cooling of the PCAs within the computer chassis/card cage assembly is usually performed by a system of fans set above and below the PCAs within the chassis, as opposed to each individual PCA maintaining its own fan. Therefore, it is imperative that the airflow throughout the system be uniform with respect to each PCA card to ensure proper cooling.
One problem with the fans being utilized in a convection fashion throughout the chassis is realized when a slot is empty. For example, an unpopulated (empty) slot creates a low-resistance passages that allows for undisturbed airflow. While, any adjoining populated (filled) slots have PCAs which act as high-resistance to the airflow. Therefore, the air will follow the path of least resistance and channel through the empty slot instead of passing through a filled slot. Thus, the job of cooling the components of the PCA is not accomplished. As a result, the reduction in the airflow between the PCAs may cause damage to the PCA cards through overheating.
At present one approach to fix the problem described above, is to add a mechanism, such as a blank PCA card, to the empty slot. The blank PCA card creates sufficient airflow resistance such that the airflow is evenly distributed throughout the system. However, one disadvantage of an added mechanism is user convenience. For example, if the user is required to add a mechanism to an empty slot each time a PCA card is removed, and the user forgets, the system will be deleteriously effected. Specifically, as previously stated, many PCAs may be damaged by the airflow channeling causing overheating of the system. In addition, the user may not realize a filler mechanism is required in the empty slot. It may also be the case that the user doesn't have a filler mechanism and thus the slot remains empty.
In addition to an airflow blocking mechanism being added to the empty slot to equalize the airflow of the system, a filler panel must also be coupled to the chassis. Conventionally, filler panels are used in conjunction with various computer chassis for electromagnetic interference (EMI) containment as well as for sealing of the computer chassis/card cage for thermal (e.g. forced airflow) cooling purposes. Specifically, in a conventional computer chassis/card cage assembly, multiple slots are available to receive a corresponding printed circuit assembly (PCA). The filler panels are attached to the computer chassis to enclose or seal off regions/slots of the computer chassis which do not have a printed circuit assembly (PCA) disposed therein. Typically, conventional filler panels are attached to the computer chassis using captive screws. The captive screws are disposed on the filler panels at locations corresponding to mounting holes residing within the computer chassis.
The location and the spacing of mounting holes within the computer chassis (and the corresponding location of the captive screws on the filler panels) are often defined by an industry standard. Typical standards include, for example, the compact peripheral component interconnect (CPCI) standard, and the VersaModular Eurocard (VME) standard. For example, the CPCI standard dictates that the gap between adjacent units (e.g. adjacent filler panels, adjacent PCAs, or a PCA and an adjacent filler panel) be nominally set at 0.30 millimeters. Unfortunately, industry standard captive screws allow the filler panel to be mispositioned by more than 1.0 millimeter. For purposes of the present application, this mispositioning with respect to the computer chassis, caused in some cases by the use of captive screws, is referred to as interference generating movement. During use, the interference generating movement of the filler panels can deleteriously prevent insertion of a PCA or a filler panel. That is, interference generating movement of one or more filler panels can result in insufficient space in a neighboring slot such that a filler panel or a PCA will not fit in the compromised gap.
At present, one approach to fix the problem described above, is to first have all of the necessary filler panels loosely connected to the computer chassis. Once all of the filler panels are in place, the filler panels are then carefully tightened to the computer chassis in order to insure that interference generating movement is reduced as much as possible. However, such a method is time-consuming, cumbersome, and lacks the desired “Design for Manufacturability (DFM).”
The problem described above is particularly egregious in light of the increased prevalence of “hot swapping.” Hot swapping refers to a process in which a PCA is added to or removed from the computer chassis without powering down the system. With hot swapping, it is imperative that interference generating movement is reduced in order to facilitate rapid and perhaps frequent removal and addition of PCAs and filler panels.
One prior art attempt to resolve the problem of interference generating movement involves customizing a computer chassis with a non-standard sheet metal interface having predefined openings formed therein. Specially designed filler panels are also employed in conjunction with the non-standard customized computer chassis. Such an approach has severe drawbacks associated therewith. For example, a non-standard customized chassis allows DFM tolerancing that makes is very difficult to hold CPCI standard specifications. Furthermore, limiting customers to the use of one particular design/maker of filler panels is not favorable.
A further drawback is the mounting method for captive screws used in conjunction with filler panel assemblies. Specifically, as stated above, a filler panel mounted to a chassis is a tight fit. In fact, if captive screws are not utilized, ensuring a proper fit between the chassis and the filler panel is extremely difficult. In addition, since a filler panel is required for each slot not occupied with any type of complete assembly (i.e. any empty slot), on any given chassis, the number of empty slots can be extensive. As such, the multiplicity of required filler panels translates into a multiplicity of captive screw mounts. For example, a keyed filler panel assembly may include an attaching device comprised of a captive screw and an underlying D-clip.
It is appreciated that each underlying D-clip has an associated per item cost. It is further appreciated that a second cost is accrued with regard to assembly. Specifically, for every part required in the assembly operation, time and labor factors must be accounted for in the assembly process. That is, time and labor requirements translate into accrued costs. As a result, the associated costs of a filler panel assembly can deleteriously effect company profit.
A further problem has arisen with regard to the removal of filler panel assemblies. Specifically, as stated above, a filler panel mounted to a chassis is a tight fit. In fact, the EMI gasket causes a friction force which helps hold a filler panel in-place. Further, the face of the filler panel is smooth with nothing to grasp. Thus, with a multiplicity of filler panels or complete assemblies mounted on a chassis, removal of a single filler panel is both difficult and time consuming.